mineral

Chalcedony Agate / Carnelian nodules in Matrix

SiO2 (Silicon Dioxide) with iron oxide inclusions

Mohs hardness: 6.5 - 7; Color: translucent yellowish-orange to reddish-brown (carnelian/chalcedony) mixed with greyish host matrix; Luster: waxy to vitreous; Cleavage: none, exhibits conchoidal fracture.

Hardness: 6
Luster: waxy to vitreous

Identified July 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluid precipitates within cavities (vesicles) of volcanic or sedimentary rocks, often incorporating iron oxides that create warm orange and reddish tints. Over time, the host rock weathers away, leaving behind weather-resistant chalcedony and agate nodules.

Uses & applications

Popular for lapidary work, gemstones, tumbling, cabochons, and decorative mineral specimens.

Geological facts

The pitted, honeycomb-like surface is characteristic of vesicular cavity fills where softer mineral matrices or surrounding volcanic material eroded away, leaving behind the harder microcrystalline quartz core.

Field identification & locations

Look for translucency around the edges when held to a light source, waxy luster, smooth groundmass texture, and high resistance to scratching (will scratch glass). Commonly found in riverbeds and gravel deposits near volcanic regions.

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